1. Field of the Invention
The present invention relates to a semiconductor device test system for testing semiconductor devices at a low cost and high efficiency.
2. Description of the Related Art
FIG. 3 shows the prior art semiconductor test system disclosed in the Dec. 20, 1991 issue of "Hardware Specifications for AF-8630 Test Burn-in Test System" in its seventh edition published by ANDO ELECTRIC CO., LTD. Shown in FIG. 3 are pallets 1, each of which is loaded with a plurality types of semiconductor devices 2 according to the type of semiconductor device, magazines 3, each for accommodating a plurality of pallets, a first shelf 4 for storing the magazines 3 and a plurality of burn-in carriers 11 loaded with no semiconductor devices 2, a first operator 5 who transports a magazine 3 on a platform truck 6 or a burn-in carrier 11 on a platform truck 13, between the first shelf 4 and an insertion unit to be described later, and burn-in boards 7 which receive semiconductor devices 2 at its test sockets 8 according to the type of semiconductor devices. The pallets 1 and the magazines 3 are intentionally depicted as a round structure in shape to discriminate them from the burn-in boards 7 and the burn-in carriers 11 in FIG. 3, and are not limited to these shapes.
Also shown are the insertion unit 9 for picking up a semiconductor device 2 from a pallet 1 loaded with semiconductor devices and placing it to a burn-in board 7 loaded with no semiconductor devices 2, an extractor unit 10 for extracting a semiconductor device 2 from a burn-in board 7 loaded with semiconductor devices 2 and placing it on a pallet 1 to be loaded with semiconductor devices 2, burn-in carriers 11 for accommodating a plurality of burn-in boards 7, and an operator 12 who transports a burn-in carrier 11 on a platform truck 13 between the insertion unit 9 or the extractor unit 10 and a TBI unit to be described later.
Further shown in FIG. 3 are a TBI (test burn-in) unit 14 for carrying out burn-in tests to the semiconductor devices 2 on a burn-in board 7 according to the type of the semiconductor devices, and a TBI host 15 connected to the insertion unit 9, extractor unit 10, and TBI unit 14, for collecting product data about the semiconductor devices 2 placed by the insertion unit 9, transmitting a test program to the TBI unit 14 based on the product data, and instructing the extractor unit 10 to extract and reject any semiconductor devices 2 identified as faulty by the test result.
The operation of the semiconductor device test system thus constructed is now discussed. Stored on the first shelf 4 is the magazine 3 in which a plurality of pallets 1 are held. Each of the pallets 1 holds a plurality of types of semiconductor devices according to the type of semiconductor devices. Also stored on the first shelf 4 is the burn-in carrier 11 that holds a plurality of burn-in boards 7, each of which is empty and prepared to be loaded with a plurality of types of semiconductor devices according the type of semiconductor device. The first operator 5 picks up from the first shelf 4 the magazine 3 holding semiconductor devices 2 of the same type, and mounts it on the platform truck 6 for transportation to the insertion unit 9. Further, the first operator 5 picks up from the first shelf 4 the burn-in carrier 11 which has no semiconductors thereon and is ready to receive the semiconductor devices of the same type, and mounts in on the platform truck 13 for transportation to the insertion unit 9. The insertion unit 9 picks up the semiconductor devices 2 from the pallet 1 and places them into the sockets 8 on the burn-in board 7.
Meanwhile, the product data about the semiconductor devices 2 on the burn-in board 7 is transmitted to the TBI host 15. The plurality of such burn-in boards 7 are held in the burn-in carrier 11. The second operator 12 picks up the burn-in carrier 11 having the semiconductor devices of the same type from the insertion unit 9, and mounts it on the platform truck 13 for transportation to the TBI unit 14.
The TBI unit 14 tests the semiconductor devices 2. The tests performed include a burn-in test, and read and write tests, for example. The TBI host 15 transmits to the TBI unit 14 a test program in accordance with the product data of the semiconductor devices 2. After the burn-in carrier 11 has undergone the tests, the second operator 12 picks them up from the TBI unit 14 and transports them on the platform truck 13 to the extractor unit 10.
The extractor unit 10 extracts the semiconductor devices 2 from the burn-in board 7 and places them on the pallet 1. Meanwhile, the TBI host 15 transmits a test result to the extractor unit 10 and any semiconductor devices 2 that are determined to be faulty are picked up and placed on a pallet 1 different from the pallet 1 on which the passed semiconductor devices 2 are placed. A plurality of such pallets 1 are accommodated in the magazine 3. The first operator 5 picks up, from the extractor unit 10, the magazine 3 having the semiconductor devices 2 that have undergone the tests, and transports it on the platform truck 6 to the first shelf 4. In the discussion above, the insertion unit 9 and the extractor unit. 10 are different units for convenience of explanation. In practice, however, an insertion/extractor unit for inserting and extracting the semiconductor devices 2 may be used. By the use of a switch, it may function as the insertion unit 9 and the extractor unit 10.
Since the semiconductor device test system is thus constructed, the semiconductor devices 2 stored on the first shelf 4 have to be tested on the TBI unit 14 on a per semiconductor device type basis. If the TBI unit 14 has the capability to test four burn-in carriers 11 at a time with its test area divided into four partitions, it will be able to concurrently handle four incoming burn-in carriers 11 having four respective different semiconductor device types 2. Thus, the ability of the TBI unit 14 is fully used. This arrangement however needs a costly TBI unit 14 having a multiple test area partitioning capability.
In its low-cost version, the TBI unit 14 may have the capability to test four burn-in carriers at a time with its test area divided into a smaller number of partitions, for example, two partitions. With this arrangement, the TBI unit 14 may make the most efficient use of its ability if two burn-in carriers 11 loaded with two respectively different semiconductor types come in at a time. The actual operation does not necessarily meet such a condition, and if three or more types of semiconductor devices are input, concurrent testing will become impossible, and the TBI unit 14 may be forced at a process yield level lower than the maximum available yield. Thus, the process efficiency of the TBI unit 14 is degraded.
Since the semiconductor devices 2 stored on the first shelf 4 and the semiconductor devices 2 that have undergone the tests have to be subjected to the insertion and extraction operations, the testing operation lacks smoothness, increasing the cost of semiconductor device testing and degrading the efficiency of semiconductor device testing.